This invention relates to an improved ball valve, of the type in which an apertured ball is rotatable to open or close the way between an inlet and an outlet.
Ball valves of this type are commonly used in oil refinery installations, and are required to withstand high fluid pressure without permitting any leakage. Such a ball valve is described in the specification of my co-pending U.S. patent application No. 691,483, now U.S. Pat. No. 4,068,822, granted Jan. 19, 1978, and has a body with coaxial inlet and outlet passages leading to and from a chamber housing a diametrically apertured ball which is rotatable, by a handle, about an axis perpendicular to that of the inlet and outlet. Resilient seal rings contact the ball on its inlet and outlet sides, the ring to the inlet side of the ball being backed by a fixed annular flange within the body, the other ring, to the outlet side of the ball, being backed by an annular insert threadedly engaged in the outlet passage. A deformable ring, lying partly in an annular groove in the outlet passage and partly in an annular rebate in the annular insert, greatly improves the sealing qualities of the assembly, being deformed, when the annular insert is screwed hard into place, to press against the peripheral part of the near sealing ring and also against the body.
The inlet and outlet passages of the ball valve are formed with tapered threads to receive correspondingly threaded inlet and outlet pipes, for optimum sealing, and a disadvantage of the ball valve described has been the difficulty encountered in the accurate longitudinal locating of the threaded insert, engaged in the tapered thread of the outlet passage.